Bus systems may be used to facilitate communication between devices. A controller area network (CAN) bus is one type of a bus system that may be used in automotive applications and in industry automation. Several nodes that are capable of sending and receiving messages (e.g., controllers, sensors, and actuators) are connected to the bus. For example, a node connected to the CAN bus may include a processing unit configured for processing sensor data, a CAN-controller for compiling messages to be transmitted on the bus or decoding received messages, and a transceiver for generating the electric signals that transmit the message on the CAN bus.
FIG. 1 illustrates a CAN bus 100. A number N of nodes 101, 102, and so forth are coupled to the CAN bus 100. Each CAN node is locally powered. The CAN bus 100 may be operated with a predetermined termination impedance (RT). To achieve the predetermined termination impedance on the bus, each node 101, 102, and so forth includes a termination impedance 110 having a resistance value of N*RT. If N nodes are connected to the bus, the total bus impedance will be RT.
A problem arises if nodes are to be added to or removed from the bus. The bus impedance may change and an impedance mismatch on the CAN bus may result.
This problem may occur in a subsea environment where the bus and the nodes connected to the bus are inaccessible. If a node is disconnected from the bus (e.g., due to failure of the node), the bus impedance will change. The change in bus impedance may be detrimental to reliable operation of the remaining nodes. As a result, communication between the different nodes may be disturbed and the whole system may need costly and time-intensive servicing.